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Jun 30, 2018
06/18

by
Luciana Ferrer

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Standard probabilistic discriminant analysis (PLDA) for speaker recognition assumes that the sample's features (usually, i-vectors) are given by a sum of three terms: a term that depends on the speaker identity, a term that models the within-speaker variability and is assumed independent across samples, and a final term that models any remaining variability and is also independent across samples. In this work, we propose a generalization of this model where the within-speaker variability is not...

Topics: Learning, Machine Learning, Statistics, Computing Research Repository

Source: http://arxiv.org/abs/1704.02346

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Sep 18, 2013
09/13

by
Phil Ferrer

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The large N limit of fermionic vectors models is studied using bilocal variables, in the framework of a collective field theory approach. The large N configuration is determined completely using only classical solutions of the model. Further, the Bethe-Salpeter equations of the model are cast as a Green's function problem. One of the main results of this work is to show that this Green's function is in fact the large N bilocal itself.

Source: http://arxiv.org/abs/hep-th/0505111v2

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Jul 20, 2013
07/13

by
F. Ferrer

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We calculate the flux of high energy gamma-rays from annihilation of neutralino dark matter in the centre of the Milky Way and the three nearest dwarf spheroidals (Sagittarius, Draco and Canis Major), using realistic models of the dark matter distribution.

Source: http://arxiv.org/abs/astro-ph/0406241v1

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Sep 18, 2013
09/13

by
Francesc Ferrer

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Ground based Atmospheric Cerenkov Telescopes have recently unveiled a TeV gamma-ray signal from the direction of the Galactic Centre. We examine whether these gamma-rays, observed by the VERITAS, CANGAROO-II and HESS collaborations, may arise from annihilations of dark matter particles. Emission from nearby dwarf spheroidals, such as Sagittarius, could provide a test of this scenario.

Source: http://arxiv.org/abs/astro-ph/0505414v1

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Sep 22, 2013
09/13

by
Jaime Ferrer

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The existance of a spin disordered ground state for the frustrated Quantum Heisenberg Antiferromagnet on a square lattice is reconsidered. It is argued that there is a unique action which is continuous through the whole phase diagram, except at the Lifshitz point, so that the Neel and helicoidal states can not coexist and there has to be an intermediate spin liquid state. To show it, a detailed study combining Spin-Wave theory, Schwinger Bosons Mean Field Theory and a scaling analysis of the...

Source: http://arxiv.org/abs/cond-mat/9209009v1

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Sep 21, 2013
09/13

by
Sebastián Ferrer

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Extending to 4 degrees of freedom a symplectomorphism used in attitude dynamics it is shown in a direct way the connection between the 4-D isotropic harmonic oscillator and the 3-D Kepler systems. This approach made transparent that only when we refer to rectilinear solutions, the {\sl bilinear relation} defining the KS transformation is needed.

Source: http://arxiv.org/abs/1011.3000v1

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Sep 22, 2013
09/13

by
Jaime Ferrer

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The characterization and evolution of a Spin Density Wave into the Quantum Neel ground state is considered in the context of a weak coupling theory of the half-filled Hubbard model. Magnetic properties obtained from this weak coupling approach in one dimension compare favorably with exact results from Bethe ansatz (BA). A study of the evolution of several length scales from weak to strong coupling is also presented.

Source: http://arxiv.org/abs/cond-mat/9410019v1

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0.0

Jun 30, 2018
06/18

by
Ramon Ferrer-i-Cancho

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The use of null hypotheses (in a statistical sense) is common in hard sciences but not in theoretical linguistics. Here the null hypothesis that the low frequency of syntactic dependency crossings is expected by an arbitrary ordering of words is rejected. It is shown that this would require star dependency structures, which are both unrealistic and too restrictive. The hypothesis of the limited resources of the human brain is revisited. Stronger null hypotheses taking into account actual...

Topics: Physics, Computing Research Repository, Computation and Language, Social and Information Networks,...

Source: http://arxiv.org/abs/1411.2645

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0.0

Jun 28, 2018
06/18

by
Ramon Ferrer-i-Cancho

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Word order evolution has been hypothesized to be constrained by a word order permutation ring: transitions involving orders that are closer in the permutation ring are more likely. The hypothesis can be seen as a particular case of Kauffman's adjacent possible in word order evolution. Here we consider the problem of the association of the six possible orders of S, V and O to yield a couple of primary alternating orders as a window to word order evolution. We evaluate the suitability of various...

Topics: Information Theory, Mathematics, Physics and Society, Physics, Computation and Language, Computing...

Source: http://arxiv.org/abs/1512.05582

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0.0

Jun 30, 2018
06/18

by
E. J. Ferrer

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Compact stars with significant high densities in their interiors can give rise to quark deconfined phases that can open a window for the study of strongly interacting dense nuclear matter. Recent observations on the mass of two pulsars, PSR J1614-2230 and PSR J0348+0432, have posed a great restriction on their composition, since their equations of state must be hard enough to support masses of about at least two solar masses. The onset of quarks tends to soften the equation of state, but due to...

Topics: Nuclear Theory, High Energy Physics - Phenomenology, Astrophysics, High Energy Astrophysical...

Source: http://arxiv.org/abs/1703.09270

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1.0

Jun 29, 2018
06/18

by
Gabriel J. Ferrer

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In this position paper, we discuss how the use of a cognitive architecture based on unsupervised clustering (the Kohonen Self-Organizing Map) enables us to meet our goals of efficient action selection in a mobile robot. This architecture provides several opportunities for human-robot interaction, and we discuss how its features facilitate these interactions.

Topics: Computing Research Repository, Robotics

Source: http://arxiv.org/abs/1602.08158

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0.0

Jun 30, 2018
06/18

by
Ramon Ferrer-i-Cancho

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Here we respond to some comments by Alday concerning headedness in linguistic theory and the validity of the assumptions of a mathematical model for word order. For brevity, we focus only on two assumptions: the unit of measurement of dependency length and the monotonicity of the cost of a dependency as a function of its length. We also revise the implicit psychological bias in Alday's comments. Notwithstanding, Alday is indicating the path for linguistic research with his unusual concerns...

Topics: Physics, Data Analysis, Statistics and Probability, Computing Research Repository, Computation and...

Source: http://arxiv.org/abs/1412.7186

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0.0

Jun 29, 2018
06/18

by
Ramon Ferrer-i-Cancho

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Here we sketch a new derivation of Zipf's law for word frequencies based on optimal coding. The structure of the derivation is reminiscent of Mandelbrot's random typing model but it has multiple advantages over random typing: (1) it starts from realistic cognitive pressures (2) it does not require fine tuning of parameters and (3) it sheds light on the origins of other statistical laws of language and thus can lead to a compact theory of linguistic laws. Our findings suggest that the recurrence...

Topics: Computation and Language, Data Analysis, Statistics and Probability, Physics, Neurons and...

Source: http://arxiv.org/abs/1605.01326

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0.0

Jun 30, 2018
06/18

by
Ramon Ferrer-i-Cancho

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The syntactic structure of a sentence can be modeled as a tree where vertices are words and edges indicate syntactic dependencies between words. It is well-known that those edges normally do not cross when drawn over the sentence. Here a new null hypothesis for the number of edge crossings of a sentence is presented. That null hypothesis takes into account the length of the pair of edges that may cross and predicts the relative number of crossings in random trees with a small error, suggesting...

Topics: Physics, Computing Research Repository, Computation and Language, Social and Information Networks,...

Source: http://arxiv.org/abs/1410.5485

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3.0

Jun 27, 2018
06/18

by
Martin Lara; Sebastián Ferrer

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Integration of Hamiltonian systems by reduction to action-angle variables has proven to be a successful approach. However, when the solution depends on elliptic functions the transformation to action-angle variables may need to remain in implicit form. This is exactly the case of the simple pendulum, where in order to make explicit the transformation to action-angle variables one needs to resort to nontrivial expansions of special functions and series reversion. Alternatively, it is shown that...

Topics: Nonlinear Sciences, Exactly Solvable and Integrable Systems

Source: http://arxiv.org/abs/1503.03358

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0.0

Jun 30, 2018
06/18

by
Ramon Ferrer-i-Cancho

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Comment on "Approaching human language with complex networks" by Cong & Liu

Topics: Physics, Computing Research Repository, Computation and Language, Social and Information Networks,...

Source: http://arxiv.org/abs/1408.1774

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Sep 17, 2013
09/13

by
Efrain J. Ferrer

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The dense core of compact stars is the natural medium for the realization of color superconductivity. A common characteristic of such astrophysical objects is their strong magnetic fields, especially those of the so called magnetars. In this talk, I discuss how a color superconducting core can generate or/and enhance the stellar magnetic field independently of a magnetohydrodynamic dynamo mechanism. The magnetic field generator is in this case a gluonic current which circulates to stabilize the...

Source: http://arxiv.org/abs/0912.0967v2

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Sep 20, 2013
09/13

by
Leonor Ferrer; Francisco Martin

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In this paper we describe a new deformation that connects minimal disks with planar ends with minimal disks with helicoidal ends. In this way, we are able to construct a family of complete minimal surfaces with helicoidal ends that contains the singly periodic genus one helicoid of Hoffman, Karcher and Wei.

Source: http://arxiv.org/abs/math/0405588v1

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Sep 17, 2013
09/13

by
Aleix Prats Ferrer

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In a recent work [1] we consider the topological expansion for the non-mixed observables (including the free energy) for the formal Cauchy matrix model. The only restriction in [1] was the fact that all the branch points have to be simple. This excludes a very interesting situation not encountered in the literature before, namely the case in which two branch points merge in such a way that no cycle is pinched. In this work we focus on this situation and derive new formulas that apply to...

Source: http://arxiv.org/abs/0912.2984v4

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Sep 18, 2013
09/13

by
Francesc Ferrer; Tanmay Vachaspati

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We show that a tangle of light superconducting strings in the Milky Way could be the source of the observed 511 KeV emission from electron-positron annihilation in the Galactic bulge. The scenario predicts a flux that is in agreement with observations if the strings are at the ~ 1 TeV scale making the particle physics within reach of planned accelerator experiments. The emission is directly proportional to the galactic magnetic field and future observations should be able to differentiate the...

Source: http://arxiv.org/abs/astro-ph/0505063v3

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Sep 17, 2013
09/13

by
V. Ferrer; I. Vainsencher

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We give formulas for the degrees of the spaces of foliations in P2 with a dicritical singularity of prescribed order. Blowing up such singularity induces, generically, a foliation with all but finitely many leaves transversal to the exceptional line; we also find the degree of the locus defined by imposing a leaf of total contact with the exceptional line.

Source: http://arxiv.org/abs/1003.6107v1

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Sep 20, 2013
09/13

by
Francesc Ferrer; Tanmay Vachaspati

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Observations of the Milky Way by the SPI/INTEGRAL satellite have confirmed the presence of a strong 511 KeV gamma-ray line emission from the bulge, which require an intense source of positrons in the galactic center. These observations are hard to account for by conventional astrophysical scenarios, whereas other proposals, such as light DM, face stringent constraints from the diffuse gamma-ray background. Here we suggest that light superconducting strings could be the source of the observed...

Source: http://arxiv.org/abs/astro-ph/0608168v1

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Sep 18, 2013
09/13

by
Francesc Ferrer; Syksy Rasanen

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We study the stability of extra dimensions in string gas cosmology at late times. Vacuum energy and, interestingly, baryons lead to decompactification after they become dynamically important. The string gas can stabilise the effect of baryons, but not that of vacuum energy. However, we find that the interplay of baryons and strings can lead to acceleration in the visible dimensions, without the need for vacuum energy.

Source: http://arxiv.org/abs/hep-th/0509225v2

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Sep 22, 2013
09/13

by
Martin Lara; Sebastián Ferrer

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The essentially unique reduction of the Euler-Poinsot problem may be performed in different sets of variables. Action-angle variables are usually preferred because of their suitability for approaching perturbed rigid-body motion. But they are just one among the variety of sets of canonical coordinates that integrate the problem. We present an alternate set of variables that, while allowing for similar performances than action-angles in the study of perturbed problems, show an important...

Source: http://arxiv.org/abs/1101.0229v1

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Sep 21, 2013
09/13

by
Fernando Sols; Jaime Ferrer

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The crossover between ideal Josephson behavior and uniform superconducting flow is studied by solving exactly the Ginzburg-Landau equation for a one-dimensional superconductor in the presence of an effective delta function potential of arbitrary strength. As the effective scattering is turned off, the pairs of Josephson solutions with equal current evolve into a uniform and a solitonic solution with nonzero phase offset. It is also argued that a microscopic description of the crossover must...

Source: http://arxiv.org/abs/cond-mat/9312005v1

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28

Sep 19, 2013
09/13

by
Efrain J. Ferrer

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The natural candidates for the realization of color superconductivity are the extremely dense cores of compact stars, many of which have very large magnetic fields, especially the so-called magnetars. In this paper we discuss how a color superconducting core can serve to generate and enhance the stellar magnetic field without appealing to a magnetohydrodynamic dynamo mechanism.

Source: http://arxiv.org/abs/0708.1618v1

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Sep 20, 2013
09/13

by
Francesc Ferrer; Christopher Spitzer

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We explore the dark matter sector in extensions of the Minimal Supersymmetric Standard Model (MSSM) that can provide a good fit to the PAMELA cosmic ray positron excess, while at the same time addressing the little hierarchy problem of the MSSM. Adding a singlet Higgs superfield, S, can account for the observed positron excess, as recently discussed in the literature, but we point out that it requires a fine-tuned choice for the parameters of the model. We find that including an additional...

Source: http://arxiv.org/abs/1002.1646v2

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36

Sep 18, 2013
09/13

by
Francesc Ferrer; Syksy Rasanen

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We discuss an inflationary scenario based on Lovelock terms. These higher order curvature terms can lead to inflation when there are more than three spatial dimensions. Inflation will end if the extra dimensions are stabilised, so that at most three dimensions are free to expand. This relates graceful exit to the number of large dimensions.

Source: http://arxiv.org/abs/0707.0499v2

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32

Jul 20, 2013
07/13

by
E. J. Ferrer

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The Ritus' $E_{p}$ eigenfunction method is extended to the case of spin-1 charged particles in a constant electromagnetic field and used to calculate the one-loop neutrino self-energy in the strong-field approximation $m_{e}^{2}\ll eB\ll M_{W}^{2}$. The implications of the obtained results for neutrino oscillations in the early Universe, assuming the existence of a sufficiently large ($m_{e}^{2}\ll eB\ll m_{\mu}^{2}$) primordial magnetic field, are discussed.

Source: http://arxiv.org/abs/hep-ph/0009304v1

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0.0

Jun 30, 2018
06/18

by
Ferrer-Santos Walter; Rittatore Alvaro

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We present a generalized version of classical geometric invariant theory \`a la Mumford where we consider an affine algebraic group $G$ acting on a specific affine algebraic variety $X$. We define the notions of linearly reductive and of unipotent action in terms of the $G$ fixed point functor in the category of $(G,\Bbbk [X])$--modules. In the case that $X=\{\star\}$ we recuperate the concept of lineraly reductive and of unipotent group. We prove in our "relative" context some of the...

Topics: Mathematics, Algebraic Geometry

Source: http://arxiv.org/abs/1406.4446

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Sep 20, 2013
09/13

by
F. Ferrer; M. Nowakowski

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In certain mild extensions of the Standard Model, spin-independent long range forces can arise by exchange of two very light pseudoscalar spin--0 bosons. In particular, we have in mind models in which these bosons do not have direct tree level couplings to ordinary fermions. Using the dispersion theoretical method, we find a $1/r^{3}$ behaviour of the potential for the exchange of very light pseudoscalars and a $1/r^{7}$ dependence if the pseudoscalars are true massless Goldstone bosons.

Source: http://arxiv.org/abs/hep-ph/9810550v1

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Sep 21, 2013
09/13

by
Walter Ferrer Santos

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Gerhard Hochschild's contribution to the development of mathematics in the XX century is succinctly surveyed. We start with a personal and mathematical biography, and then consider with certain detail his contributions to algebraic groups and Hopf algebras.

Source: http://arxiv.org/abs/1104.0335v1

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Sep 23, 2013
09/13

by
Efrain J. Ferrer

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In this talk I review some of the main findings on magnetism in color superconductivity. The physical characteristic of the different phases that are reached by increasing the applied magnetic field in a three-flavor color superconductor at asymptotically high densities are discussed. A mechanism to boost a seed magnetic field in high-dense quark matter is presented. Also, it is shown how a magnetic field can be generated in a color superconductor at moderate densities. Possible implications of...

Source: http://arxiv.org/abs/1110.2081v1

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Sep 23, 2013
09/13

by
Josep Domingo-Ferrer

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The purpose of statistical disclosure control (SDC) of microdata, a.k.a. data anonymization or privacy-preserving data mining, is to publish data sets containing the answers of individual respondents in such a way that the respondents corresponding to the released records cannot be re-identified and the released data are analytically useful. SDC methods are either based on masking the original data, generating synthetic versions of them or creating hybrid versions by combining original and...

Source: http://arxiv.org/abs/1202.6009v1

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30

Sep 22, 2013
09/13

by
Sebastián Ferrer; Martin Lara

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The Hamilton-Jacobi equation in the sense of Poincar\'e, i.e. formulated in the extended phase space and including regularization, is revisited building canonical transformations with the purpose of Hamiltonian reduction. We illustrate our approach dealing with orbital and attitude dynamics. Based on the use of Whittaker and Andoyer symplectic charts, for which all but one coordinates are cyclic in the Hamilton-Jacobi equation, we provide whole families of canonical transformations, among which...

Source: http://arxiv.org/abs/0906.5312v2

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Sep 22, 2013
09/13

by
Efrain J. Ferrer

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In this talk I will discuss how the in-medium magnetic field can influence the gluon dynamics in a three-flavor color superconductor. It will be shown how at field strengths comparable to the charged gluon Meissner mass a new phase can be realized, giving rise to Abrikosov's vortices of charged gluons. In that phase, the inhomogeneous gluon condensate anti-screens the magnetic field due to the anomalous magnetic moment of these spin-1 particles. This paramagnetic effect can be of interest for...

Source: http://arxiv.org/abs/1004.0733v1

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Sep 18, 2013
09/13

by
Esther Ferrer Ribas

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In 1999 the LEP experiments collected data at centre of mass energies between 192 and 202 GeV for about 900 pb-1 integrated luminosity. Combined results are presented for the search for the Standard Model Higgs boson. No statistically significant excess has been observed when compared to Standard Model background expectation which can be translated into a lower bound on the mass of the Higgs boson at 107.9 GeV/c^2 at 95 % confidence level.

Source: http://arxiv.org/abs/hep-ex/0012026v1

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26

Sep 17, 2013
09/13

by
Viviana Ferrer; Israel Vainsencher

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It is known after Jouanolou that a general holomorphic foliation of degree $\geq2$ in projective space has no algebraic leaf. We give formulas for the degrees of the subvarieties of the parameter space of one-dimensional foliations that correspond to foliations endowed with some invariant subvariety of degree 1 or 2 and dimension $\geq1$.

Source: http://arxiv.org/abs/1003.3997v1

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2.0

Jun 26, 2018
06/18

by
Josep Domingo-Ferrer; Krishnamurty Muralidhar

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There are currently two approaches to anonymization: "utility first" (use an anonymization method with suitable utility features, then empirically evaluate the disclosure risk and, if necessary, reduce the risk by possibly sacrificing some utility) or "privacy first" (enforce a target privacy level via a privacy model, e.g., k-anonymity or epsilon-differential privacy, without regard to utility). To get formal privacy guarantees, the second approach must be followed, but...

Topics: Databases, Computing Research Repository, Cryptography and Security

Source: http://arxiv.org/abs/1501.04186

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39

Sep 23, 2013
09/13

by
Katherine Jones-Smith; Francesc Ferrer

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The late-time accelerated expansion of the universe could be caused by a scalar field that is screened on small scales, as in chameleon or symmetron scenarios. We present an analogy between thin shell configurations of such scalar fields and electrostatics, which allows calculation of the field profile for general extended bodies. Interestingly, the field demonstrates a `lightning rod' effect, where it becomes enhanced near the ends of a pointy or elongated object. Drawing from this...

Source: http://arxiv.org/abs/1105.6085v3

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59

Sep 22, 2013
09/13

by
F. Ferrer; J. A. Grifols

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We reexamine the limits on the gravitino mass supplied by the muon anomaly in the frame of supergravity models with a superlight gravitino and a superlight scalar S and a superlight pseudoscalar P.

Source: http://arxiv.org/abs/hep-ph/9704444v1

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30

Sep 22, 2013
09/13

by
F. Ferrer; J. A. Grifols

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Using dispersion theoretic techniques, we consider coherent long range forces arising from double pseudoscalar exchange among fermions. We find that Yukawa type coupling leads to $1/r^3$ spin independent attractive potentials whereas derivative coupling renders $1/r^5$ spin independent repulsive potentials.

Source: http://arxiv.org/abs/hep-ph/9805477v1

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Sep 23, 2013
09/13

by
Pere Menal-Ferrer; Joan Porti

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For an oriented finite volume hyperbolic 3-manifold M with a fixed spin structure \eta, we consider a sequence of invariants {\tau_n(M; \eta)}. Roughly speaking, {\tau_n(M; \eta)} is the Reidemeister torsion of M with respect to the representation given by the composition of the lift of the holonomy representation defined by \eta, and the n-dimensional, irreducible, complex representation of SL(2,C). In the present work, we focus on two aspects of this invariant: its asymptotic behavior and its...

Source: http://arxiv.org/abs/1110.3718v2

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Sep 23, 2013
09/13

by
F. Ferrer; J. A. Grifols

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We study the effect of a photon background at finite temperature $T$ on the Van der Waals interactions among neutral bodies. It turns out that the long-range Casimir-Polder force is unaffected for distances much less than $T^{-1}$ and strongly enhanced for distances much above $T^{-1}$.

Source: http://arxiv.org/abs/hep-ph/9904394v1

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24

Sep 22, 2013
09/13

by
F. Ferrer; J. A. Grifols

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We explore the consequences of Bose-Einstein condensation on two-scalar-exchange mediated forces among bodies that sit in a boson gas. We find that below the condensation temperature the range of the forces becomes infinite while it is finite at temperatures above condensation.

Source: http://arxiv.org/abs/hep-ph/0001185v1

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Sep 19, 2013
09/13

by
Lucas Fernández-Seivane; Jaime Ferrer

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We analyze the impact of the magnetic anisotropy on the geometric structure and magnetic ordering of small atomic clusters of palladium, iridium, platinum and gold, using Density Functional Theory. Our results highlight the absolute need to include self-consistently the spin orbit interaction in any simulation of the magnetic properties of small atomic clusters, and a complete lack of universality in the magnetic anisotropy of small-sized atomic clusters.

Source: http://arxiv.org/abs/cond-mat/0610879v2

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Sep 23, 2013
09/13

by
Pere Menal-Ferrer; Joan Porti

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Given a finite volume hyperbolic 3-manifold, we compose a lift of the holonomy in SL(2,C) with the n-dimensional irreducible representation of SL(2,C) in SL(n,C). In this paper we give local coordinates of the SL(n,C)-character variety around this representation. As a corollary, this representation is isolated among all representations that are unipotent at the cusps.

Source: http://arxiv.org/abs/1111.4338v1

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35

Sep 21, 2013
09/13

by
F. Ferrer; J. A. Grifols

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Scalar mediated interactions among baryons extend well above the Compton wavelength, when they are embedded in a Bose-Einstein condensate composed of the mediating particles. Indeed, this non-trivial environment results in an infinite-ranged interaction. We show that if the Dark Matter of the Universe is composed of such a condensate, the imprints of an interaction between baryonic and Dark Matter could be manifest as anomalies in the peak structure of the Cosmic Microwave Background.

Source: http://arxiv.org/abs/astro-ph/0407532v2

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Sep 23, 2013
09/13

by
M. Bertola; A. Prats Ferrer

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Recently the correlation functions of the so-called Itzykson-Zuber/Harish-Chandra integrals were computed (by one of the authors and collaborators) for all classical groups using an integration formula that relates integrals over compact groups with respect to the Haar measure and Gaussian integrals over a maximal nilpotent Lie subalgebra of their complexification. Since the integration formula a posteriori had the same form for the classical series, a conjecture was formulated that such a...

Source: http://arxiv.org/abs/0801.3452v1

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Sep 21, 2013
09/13

by
Walter Ferrer Santos; Alvaro Rittatore

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In this paper we generalize some constructions and results due to Cayley and Hilbert. We define the concept of $\Omega$--process for an arbitrary algebraic monoid with zero and unit group $G$. Then we show how to produce from the process and for a linear rational representation of $G$, a number of elements of the ring of $G$-invariants, that is large enough as to guarantee its finite generation. Moreover, we give an explicit construction of all $\Omega$-processes for general reductive monoids...

Source: http://arxiv.org/abs/math/0508436v1